Technical Abstract:
Peach tree short life (PTSL) is reportedly caused by a predisposition of trees to bacterial canker (Pseudomonas syringae pv. syringae van Hall), cold injury, or a combination of both, that is the consequence of root feeding by the ring nematode, Mesocriconema xenoplax. Certain micronutrients such as nickel (Ni) are effective in managing plant diseases caused by fungi, bacteria, or nematodes (Meloidogyne sp) and are also essential mineral elements. The ability of postplant nickel (Ni) foliar application to suppress M. xenoplax population density and thereby prolong survival of peach trees on a PTSL site was investigated from 2004-2011. Plots consisted of three treatments: i) Ni [foliar applied]; ii) methyl bromide fumigation (MBr); and iii) an untreated control. Peach trees (‘Dixiland’ on Nemaguard rootstock) were planted into all plots in March 2005 and the foliar Ni treatment was applied three times in 2005 and 2006. Nickel did not detectably suppress M. xenoplax populations as compared to MBr fumigation. The effectiveness of MBr fumigation, as measured by M. xenoplax population density, collapsed 27 months after orchard establishment. Trees receiving multiple foliar Ni applications at 0.45 g·L-1 over two years, while exposed to M. xenoplax, exhibited greater (P < 0.01) PTSL mortality than trees growing in untreated or MBr fumigated plots. These results suggest that foliar applications of Ni to peach trees, growing on a PTSL site, can disrupt tree metabolic/physiological processes sufficient to increase incidence of PTSL tree mortality and should therefore be used with caution in commercial orchards.